Diagnosis and treatment of conditions affecting the brain are among the most difficult and complex problems that face the medical profession. The brain is a complex and delicate soft multi-component tissue structure that controls bodily functions through a complex neural network connected to the rest of the body through the spinal cord. The brain and spinal cord are contained within and protected by significant bony structures, e.g., the skull and the spine. Given the difficulty of accessing the brain through the hard bony protective skull and the delicate network and complex interactions that form the neural communication network contained within the brain that define the human body's ability to carry on its functions of speech, sight, hearing, functional mobility, reasoning, emotions, respiration and other metabolic functions, the diagnosis and treatment of brain disorders presents unique challenges not encountered elsewhere in the body.
For example, abnormalities such as intracranial cerebral hematomas (ICH), abscesses, glioblastomas (GB), metastases (mets) and functional diseases manifest themselves in the intraparenchymal subcortical space (i.e., the white matter) of the brain are particularly challenging to access, let alone treat. The ventricles of the brain contain eloquent communication structures (neural network) which are located in the subcortical space, called fiber tracts and fascicles. Thus, traditionally, unless the ICH, GB, and/or mets were considered anything but “superficial,” such conditions have been considered challenging to access, simply because getting to the abnormality ICH, GB and/or mets are considered just as damaging as letting the condition take its course. Similarly, tissue abnormalities such as tumors, cysts and fibrous membrane growths which manifest within the intraventricular space of the brain are considered challenging to safely access and often inoperable, due to their locations within the brain.
In order to assist in diagnosis and subsequent treatment of brain disorders, clear, accurate imaging of brain tissue through the skull is required. In recent years significant advances have been made in imaging technology, including stereotactic X-ray imaging, Computerized Axial Tomography (CAT), Computerized Tomographic Angiography (CTA), Position Emission Tomography (PET) and Magnetic Resonance Imaging (MRI), Diffusion Tensor Imaging (DTI) and Navigation systems (instrument position tracking systems). These imaging devices and techniques permit the surgeon to observe conditions within the brain in a non-invasive manner without opening the skull, as well as provide a map of critical structures surrounding an area of interest, including structures such as blood vessels, membranes, tumor margins, cranial nerves, including fiber tracts and fascicles. If an abnormality is identified through the use of one or more imaging modalities and/or techniques, it may be necessary or desirable to biopsy or remove the abnormality.
Once a course of action has been determined based upon one or more imaging techniques, a surgical treatment may be necessary or desired. In order to operate surgically on the brain, access must be obtained through the skull and delicate brain tissue containing blood vessels and nerves that can be adversely affected by even slight disturbances. Therefore, great care must be taken in operating on the brain so as not to disturb delicate blood vessels and nerves to prevent adverse consequences resulting from a surgical intervention.
Traditionally, accessing abnormalities which manifest in deeper spaces within the brain has meant a need for a surgery that creates a highly invasive approach. In some instances, in order to obtain access to target tissue, a substantial portion of the skull is removed and entire sections of the brain are retracted to obtain access. For example, surgical brain retractors are used to pull apart or spread delicate brain tissue, which can leave pressure marks from lateral edges of the retractor. In some instances, a complication known as “retraction injury” may occur due to use of brain retractors. Of course, such techniques are not appropriate for all situations, and not all patients are able to tolerate and recover from such invasive techniques.
It is also known to access certain portions of the brain by creating a burr hole craniotomy, but only limited surgical techniques may be performed through such smaller openings. In addition, some techniques have been developed to enter through the nasal passages, opening an access hole through the occipital bone to remove tumors located, for example, in the area of the pituitary. These approaches are referred to as Expanded Endonasal Approaches (EEA) and were pioneered by one of the inventors of this disclosure.
A significant advance in brain surgery is stereotactic surgery involving a stereotactic frame correlated to stereotactic X-ray images to guide a navigational system probe or other surgical instrument through an opening formed in the skull through brain tissue to a target lesion or other body. A related advance is frameless image guidance, in which an image of the surgical instrument is superimposed on a pre-operative image to demonstrate the location of the instrument to the surgeon and trajectory of further movement of the probe or instrument.
In recent years, surgical access systems have been developed to provide access to previously difficult to access areas. One such prior art system is shown in FIGS. 1A-1C. System 10 includes a retractor 20 and an introducer 40. Introducer 40 includes a cone-shaped distal end 42 with an opening 52 therein (best seen in FIG. 1C). The cone-shaped distal end is configured to be a generally blunt, flat surface. With introducer 40 positioned within retractor 10, system 10 is inserted into brain tissue, thereby pushing brain tissue away while providing access to an area of interest. Once system 10 is delivered to the area of interest, retractor 10 is rigidly fixed in position. More specifically, retractor 10 is fixed in space with the use of a standard or conventional neurosurgical fixation device. Once, retractor 10 is fixed in place, introducer 40 is then removed from retractor 10, while leaving retractor 10 in its fixed place, thereby creating a pathway through the brain tissue.
While access system 10 may provide a manner to access certain brain tissue, the blunt shaped distal end of can actually cause transient or even permanent deformation and trauma of delicate tissue structures which can manifest itself in temporary or permanent neurological deficits after surgical cytoreduction due to damage of blood vessels, cranial nerves, fiber tracts and fascicles. Opening 52 may cause coring of tissue, also leading to damage of the tissues and structures as introducer 40 is pushed through tissue. Further, by rigidly fixing the placement of retractor 10, manipulation of retractor 10 is impeded and requires constant attention by loosening and retightening to re-position for even micro-movement of the retractor 10, thereby lengthening procedure time.
Another issue that needs to be addressed is visibility. Typically when employing an access system in a surgical procedure, it is often like operating in a poorly lit tunnel. To provide illumination, it is known to place a light source within the introducer sheath, such as an endoscope. However, when using an endoscope, the light source takes up a significant amount of working space within the introducer sheath, thus reducing the functional working area for other instruments, as well as minimizing the ability to move other instruments within the surgical site.
Alternatively, light must be delivered from a remote or external location, such as a microscope or exoscope. However, in the case of microscopes and exoscopes, the external light source is often blocked by the surgeon and/or instruments in the surgical field. At a minimum, the effectiveness is greatly diminished at the distal end of the introducer sheath where the actual surgical work and/or treatment is occurring, and where effective visualization is needed the most.
Notwithstanding the foregoing advances in imaging technology and both frame and frameless stereotactic image guidance techniques, there remains a need for improved surgical techniques and apparatus for operating on brain tissue, including mechanisms for holding the surgical access system in place that allows for effective visualization, but allows some selective movement of the surgical access system, as needed.